The present invention relates to garments which protect the wearer from hazardous environmental conditions and, more particularly, to garments which provide the wearer with protection from extreme ambient conditions.
Protective garments are designed to shield the wearer from a variety of environmental hazards, and firefighter garments are representative of such garments. For example, a typical firefighter garment includes an outer shell and an inner liner including a moisture barrier and a thermal barrier. The outer shell consists of a woven aramid material such as NOMEX, KEVLAR (both trademarks of E.I. DuPont de Nemours & Co., Inc.) or a NOMEX/KEVLAR blend, or a woven polybenzamidazole ("PBI") and aramid polymer fabric blend. Fabrics of such materials provide resistance to abrasion and some thermal protection.
The thermal barrier may comprise a layer of NOMEX and KEVLAR fibers, or a batting of such fibers, often quilted to a lightweight NOMEX face cloth. The batting of the thermal barrier traps air and possesses sufficient loft to provide the necessary thermal resistance, and the face cloth protects the thermal liner from abrasion by the wearer.
Moisture resistance is provided by a membrane of expanded polytetrafluoroethylene ("PTFE") material, such as GORE-TEX (a trademark of W. L. Gore & Associates, Inc.), bonded adhesively to a fabric substrate of a NOMEX and KEVLAR blend. The GORE-TEX membrane material has microscopic openings which permit the transport of moisture vapor, thereby allowing perspiration moisture vapor of the wearer to escape outwardly, but are sufficiently small to prevent liquid moisture from the ambient, which soaks through the outer shell (or enters through sleeve or neck openings), from passing through to the wearer.
The aforementioned ensemble possesses acceptable abrasion, thermal and moisture resistance properties. The conventional arrangement of the components within the garment is such that the moisture barrier layer is positioned between the thermal liner and the outer shell. This is necessary to prevent the batting material of the thermal liner from absorbing moisture from the ambient, which would add to the overall weight of the garment and possibly reduce its loft and thermal resistance characteristics.
A disadvantage with such an arrangement is that the presence of the thermal liner between the moisture barrier and the wearer acts as a barrier which. inhibits free flow of perspiration moisture vapor from the wearer to and through the moisture barrier layer. Consequently, in high activity or stress situations, perspiration moisture vapor generated by the wearer may become trapped within the thermal liner, thus wetting the thermal liner, which adds weight to the garment and lowers the TPP (Thermal Protection Property) of the thermal liner.
Another disadvantage with such prior art garments is that the additional bulk and loft provided by such fabric thermal liners inhibits the freedom of movement of the wearer, producing a "hobbling effect," and requires the use of a face cloth, which increases the cost of the garment. The former disadvantage increases the stress imposed on the wearer in a situation requiring high activity, and accelerates the onset of fatigue.
Another type of firefighter garment, disclosed in Aldridge et al. U.S. Pat. No. 5,136,723, utilizes a thermal liner consisting essentially of a layer or layers of open mesh fabric. In addition to trapping a layer of air between the wearer and the shell of that garment, the open apertures promote heat and perspiration vapor transfer from the wearer's body. However, since such mesh fabric absorbs liquid moisture, it is preferable to place such a thermal liner inside of the moisture barrier; that is, between the wearer and the moisture barrier. Consequently, such a mesh barrier may impede the outward transport of moisture vapor somewhat.
For a protective garment to be suitable for use as a firefighting garment, the garment must meet the National Fire Protection Association 1971 Standard (hereinafter "N.F.P.A. 1971 Standard"). The N.F.P.A. 1971 Standard includes a requirement that a component of such garment withstand a temperature of 500.degree. F. for 5 minutes in a forced air oven. A component subjected to such a temperature for such a time cannot melt, drip, separate or ignite, nor can it shrink more than 10%. Additionally, all garment layers combined must provide a thermal protection performance ("TPP") rating of at least 35.
"Neoprene" is a name for a type of synthetic rubber comprising polychloroprene. Neoprene alone does not meet the N.F.P.A. 1971 Standard for flame and heat resistance and therefore is not sufficiently flame and heat resistant to be used in a firefighter garment. But neoprene can be made more flame and heat resistant by adding a chemical such as antimony oxide during the compounding process. Several prior art patents, such as U.S. Pat. No. 2,981,954 to Garbellano, U.S. Pat. No. 5,054,125 to Snedeker, U.S. Pat. No. 4,034,417 to Ellis and U.S. Pat. No. 5,021,280 to Farnworth, disclose thermal liners for various garments that include a layer of neoprene material. But these prior art patents do not disclose that the neoprene material has been treated to increase its flame and heat resistance.
U.S. Pat. No. 2,976,539 to Brown Jr. discloses a cold weather garment comprising at least two sheets of heat insulating material, such as expanded closed-cell cellular rubber and rubberlike material or plasticized polyvinyl chloride material. Such materials are not suitable for use in a firefighter garment, however, because, when incorporated into a component of a coat, such component does not possess sufficient flame and heat resistance to meet the N.F.P.A. 1971 Standard.
Accordingly, there is a need for a firefighting garment in which the transport of moisture vapor generated by the perspiration of the wearer is permitted to flow freely to and through the thermal barrier; which is relatively thin and light in weight, yet provides adequate thermal protection; which is inherently able to withstand a temperature of 500.degree. F. for at least 5 minutes; and which minimizes the restriction of movement and hobbling effect characteristic of insulated garments.